Periodic and Chaotic Current Oscillations at a Copper Electrode in an Acetate Electrolyte

Periodic and chaotic current oscillations are observed uring electrodissolution of copper in a pH 3.5 sodium acetate/ acetic acid buffer under potentiostatic conditions using a rotating copper disk electrode. Periodic or chaotic oscillations are observed epending on the applied potential and electrode rotation rate. The oscillations arise after the formation and dissolution of an acetate salt film precursor to oxide passivation. The nature and composition of the surface films were examined using scanning electron microscopy and x-ray powder diffraction data. Nonlinear dynamic analysis methods have been used to show the existence of deterministic chaos. Time series data of the chaotic oscillations were used to generate a return map that appears to be one-dimensional. The chaotic attractor was reconstructed in a three-dimensional state space using the method of time delays and the largest Lyapunov exponent was calculated and was positive for the chaotic oscillations indicating a sensitive dependence on initial conditions characteristic of deterministic chaos. Interest in the investigation of electrochemical oscilla-tions z3 has been renewed partly as a result of research in nonlinear dynamics and chemical chaosJ Oscillations have been observed in many types of electrochemical processes including both anodic and cathodic reactions. Hudson an